Gear oil change for 1000 EUR at the friendly

Today I brought my fat (V6) after 30,000 kilometers driven for inspection. So far there are no major problems, only with fast acceleration there is a squeak noise during the gear change, which takes about half a second. The workshop manager was well known this problem: “Change gear oil, then it is over.” After a few hours a call came: “…costs inclusive labor fee about 1000 EUR”. How serious is the noise to take? Can something go wrong n? If so, is there an alternative to the EUR 1000 investment? PHAETONPHIL